This seems to me to be some arbitrary way of staying conservative.
High altitude research is NOT an early 80s affair, I don't even know about
any such research during the 80s.

The Sierra Wave project was done during the 50s in the Owens Valley of Ca
with very old gliders that have been flown to 45000ft, altitudes at which,
according to this calculation, they would barely be able to fly.
However, curiously enough none of them flutter themselves to pieces.

To make a long story short :
-Look at the ASI on any turboprop or even some turbocharged aircraft, and
you will see that they fly at TAS much faster than the VNE painted on their
ASI.

Example : Twin Commander, VNE=255Kt (it's on it's ASI), Cruise TAS = 280Kt
to 300Kt.

The same holds true for all airplanes that fly up to the 20s and higher,
which aviation has been doing since WWII.


Look at the manual of some gliders, that do have the limitation on IAS with
Altitude.
You will see that the table of IAS is not correcting the VNE as a TAS value.

Nowhere in aviation VNE is considered a TAS value.


"W.J. (Bill) Dean (U.K.)." wrote in message
...
No.

The BGA have produced a book published 2002 by A & C Black, London titled
"Gliding - The British Gliding Association Manual", ISBN 0-7136-5947-5
(not to be confused with the book "Gliding" by Derek Piggott published in
about 1958 and now I think in its 6th edition).

This book covers the technical knowledge which the BGA thinks glider
pilots
should have, and is required reading for BGA rated instructors. The main
author is Steve Longland, and he had input from many others.

In chapter 5 "The placard, structure and flight limitations" there is a
section starting on p.155 "The effects of changes in air density".
In this section an explanation is given as to why the Vne is related to
True
Air Speed and not to Indicated Air Speed. I do not claim to fully
understand it myself, but I certainly intend always to obey.
The conclusion is:
"Avoiding flutter.
"The practical rule of thumb is that you should reduce the glider's Vne by
"1.5% for every 1,000ft above sea level. If your glider's Vne is 128kt,
"then at 20,000ft the ASI reading corresponding to TAS of 128kt is 90kt,
"and at 30,000ft it will be 70kt. ....."

If you read the earlier section in the same chapter about test flying, you
will see that the glider is not tested to Vd (Design dive speed) but only
to
Vdf (Demonstration design speed) which is 95% of Vd and that the placard
speed Vne is 90% of Vd.
To quote from the book: "If the glider's Vne is 130kt, it has only ever
been
6.5kt faster, once, when it was new, in ideal conditions, and flown by a
specially trained test pilot."

If anyone thinks this is wrong, could we please have a reasoned argument
and
not just abuse.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"Arnold Pieper" wrote in message
om...

Gents,

As far as the pilot is concerned, VNE is always read directly as an IAS
limit, that's why it's painted on the ASI as a radial line.
I've never seen any remarks about VNE as "VNE is XXX at Sea Level at
ISA".
There is no such thing.

VNE is always good as an Indicated figure, except at altitudes and
airspeeds where compressibility comes into play, in which case MMO
(Maximum Mach Operating speed) becomes the limiting factor, usually well
above our speeds. That happens at a certain altitude, up to which the
pilot uses the Indicated VNE as a limit, then after that the MMO.


Exception :
Certain models of sailplanes have limitations in IAS with altitude for
various reasons, (Flutter is not the only factor in determining VNE).
When a sailplane does have this limitation, it will be expressed so in
their manuals, and there will be a table of limiting IAS x Altitude.

The Jantar Std 2 is not one of these, so, VNE is good as an IAS as high
as
it will go.

The bottom-line is that it dependent on each design, but VNE is not a
TAS
figure, whoever told you so, doesn't know what he/she is talking about.

AP